Does a circuit with Positive ground output negative voltages? negative DC offset? waveforms below the zero reference?

Does a circuit with Negative ground output Positive voltages? Positive DC offset? waveforms above the zero reference?

 

in general yes.

 

well... I dont think it can be generalized...

The out put is with respect to the ground.

If the out put is supposed to be negetive with respect to the ground, output will be more negetive if the ground is negetive (with respect to some arbitraty ground)

This is similar to the LM317 which is a floating IC. The input and output difference should not be >40v.

even lm 78xx can be used as variable voltage sources if they are wired up as floating.... I saw this in the application hints sention of the datasheet.

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Bharath Bhushan Lohray.
M.Sc. Electronics.

 

lord loh.

i think you missed the point. you are mixing floating and grounded systems. question was for grounded circuits only. akg is right.
unless output is isolated or larger than supply voltage, circuits with positive ground will be negative relative to ground.

 

Sorry I do not follow.

Can I get a sompel example circuit.... :? :?

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Bharath Bhushan Lohray.
M.Sc. Electronics.

 

use simple 555 oscillator as a test circuit, make two of them and power each from separate 9V battery. connect batteries like dual voltage source (connect positive from second battery to negative of the first battery).
This will be the ground terminal. connect BLACK probe of your multimeter to it. connect RED probe to the output of the first 555 chip all readings will be positive. leave black probe connected to ground and touch with red probe output of second circuit. reading will be negative.

now remove first battery and 555 circuit but leave positive rail of second battery as ground reference. readings will still be negative.

things can get different in some cases like if the output of the circuit is isolated (it's a whole new circuit) or if the output signal is larger than supply source (you use output of 555 oscillator to drive charge pump to make voltage higher than battery from which is powered). for example if the output is 60VDC when measured to 555 ground (!), it will be some 51VDC when measured from ground because positive terminal of the 9V battery is grounded.

 

The question is too general and the answer must be of the same type.
Output signal polarity can be any, generally it does not depend on how supply voltage is grounded.

 

So if i make a 555 timer with positive ground the Pulses polarity will be negative voltages like -5 volt peak?

If i make a 555 timer with negative ground the pulse polarity will be positive volts like +5 volt peak?

 

bloki, that's true for loads. he just needs to understand difference so he can troubleshoot circuits. this is why he is asking signal level to ground reference. guys, please, stop confusing him...

walters,

you got it, the level will not really be rail to rail (I guess you had 5VDC source in mind) because there is some drop on output transistors.
see following example and note that a and b are not necessarily symetrical:

Attached Images

gnd.gif (5.0 KB, 414 views)

 

I am afraid he will ask answers for let's say 100 circuits and learn each particular circuit. Then he will imagine that he understand the problem.

 

...because nobody ever learns by asking questions; right, Bloki? [/sarcasm]

Walters, looks like you're getting the hang of this waveform stuff. 8)

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Think of a "ground" as a reference point. Let's ignore what it outputs.

The terms that are more commonly used are VCC, and Ground. Ground means a direct connection to the -ve side of the battery. VCC means a connection to the +ve side of the battery. VCC and Ground are two common terms used in digital circuits.

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yeah.. he is still surfing on the wave(form) .

 

Thanks alot guys for the pictures and help

If ground is a reference then Negative ground would be Zero volts but with positive ground it will be VCC lets just say +5volts

So if ground is the reference and positive ground then ground is +5volts

If i have a input of +5 volt pulses going into a Positive ground circuit then it will take the +5 volt pulses and output a (-)5 volts because the ground is reversed like a mirror?

Or it takes the +5 volts and outputs zero to -5 volts?

 

even though u thanked all ...... the rest of the post makes me feel that u r in still doubt about the concept of ground. afterall this is not a difficult concept .


ok..oen more type of explanation .
consider a building with two floor viz ground(consider as electrical ground) and first floor(consider as vcc) ..
'A' is standing at the ground floor and 'B' is standing at the first floor .

A says that B is 2Mtr above(+v) me . but B says that A is 2Mtrs below(-v) me
and if C is standing on top of Everest , C says that A and B are below(-v) me ..
got the concept..??

It is just that from where we look (measure) the height (voltage).